Effect of Intensive Cropping and Fertilizer Use on the Inorganic Forms of Phosphorus in a Typic Ustochrept Soil

An Investigation was made to see the affect of seven years of multiple cropping and soil test based fertilizer use on the inorganic forms of phosphorus in a Typic Ustochrept soil. Under unmanured cultivation. the depletion of the phosphorus forms as compared to fallow soil. followed the order reductant soluble-P (39.4%) iron-P (22.7%) > saloid bound-P (22.0%) aluminium P (15.2%) calcium P (9.2%). Nitrogen alone further accelerated the ines of inductant soluble P. Addition of phos-phate raised the level of all the forms including the occluded-P. FYM enhanced the saloid bound form and superphosphate thes of Al P. Tharo was a progressive huild up of P in aluminium bound and reductant soluble fraction with the raise in graded doses of phosphate.